Slip flow in elliptic microducts with constant heat flux

This paper outlines a numerical model for determining the dynamic and thermal performances of a rarefied fluid flowing in a microduct with elliptical cross-section. A slip flow is considered, in laminar steady state condition, in fully developed forced convection, with Knudsen number in the range 0.001-0.1, in H1 boundary conditions. The velocity and temperature distributions are determined in the elliptic cross-section, for different values of both aspect ratio γ and Knudsen number, resorting to the Comsol Multiphysics software, to solve the momentum and energy equations. The friction factors (or Poiseuille numbers) and the convective heat transfer coefficients (or Nusselt numbers) are calculated and presented in graphs and tables. The numerical solution is validated resorting to data available in literature for continuum flow in elliptic cross-sections (Kn = 0) and for slip flow in circular ducts (γ = 1). A further benchmark is carried out for the velocity profile for slip flow in elliptical cross-sections, thanks to a recent analytical solution obtained using elliptic cylinder coordinates and the separation of variables method. The Poiseuille and Nusselt numbers for elliptic cross-sections are discussed. The results may be used to predict pressure drop and heat transfer performance in metallic microducts with elliptic cross-section, produced by microfabrication for microelectromechanical systems (MEMS)

Influence of Outdoor Air Conditions on the Air Source Heat Pumps Performance

Abstract The purpose of the present work is the investigation of the effect of the outdoor air temperature and relative humidity on the performance of an air heat pump, when the reverse-cycle defrosting is considered. The frost formation process has been analyzed by developing a simplified model which relates the number of defrost cycles to the outdoor air conditions. Moreover the energy consumption due to the defrosting has been taken into account in the evaluation of the heat pump performance. The results, carried out for many Italian sites, point out that the outdoor air conditions play an important role in determining the amount of defrost cycles; however the frost formation is mainly affected by the relative humidity. The analysis highlights also that the defrosting contribution on the heat pump performance is not negligible when the heat pump that operates in wet weather, although cold; in these conditions the hourly COP may be reduced by up to 20%. However, this effect becomes less relevant, but not negligible, when the seasonal heat pump performance is evaluated; the maximum decrease of SCOP, observed for the all analyzed cases, is less than 13%

Custom-Made Implants in Ankle Bone Loss: A Retrospective Assessment of Reconstruction/Arthrodesis in Sequelae of Septic Non-Union of the Tibial Pilon

Background and Objectives: Treating segmental tibial and ankle bone loss after radical surgery for chronic osteomyelitis is one of the most challenging problems encountered by orthopaedic surgeons. Open tibia and ankle fractures occur with an incidence of 3.4 per 100,000 and 1.6 per 100,000, respectively, and there is a high propensity of developing fracture-related infection with associated chronic osteomyelitis in patients. Segmental tibial and ankle bone loss have recently received new and improved treatments. Materials and Methods: Above all, 3D printing allows for the customization of implants based on the anatomy of each patient, using a personalized process through the layer-by-layer deposition of materials. Results: This article presents different cases from the authors' experience. Specifically, four patients suffered tibia and ankle fractures and after radical surgery for chronic osteomyelitis combined with high-performance antibiotic therapy underwent ankle reconstruction/arthrodesis with custom-made tibial spacers. Conclusions: Thanks to 3D-printed patient-specific devices, it is possible to perform surgical procedures that, for anatomical reasons, would have been impossible otherwise. Moreover, an improvement in overall functionality and an important reduction in pain were shown in the last follow-up in all patients

Case report of Usutu virus infection in an immunocompromised patient in Italy, 2022

Usutu virus (USUV) is an arthropod-borne flavivirus emerged in Africa in 1950s and in Eruope in 1990s causing a massive number of birds' deaths. The role of USUV as human pathogen has been only recently hypothesized and cases of USUV infection in humans remain limited and often related to immunocompromised subjects. Herein, we report a case of USUV meningoencephalitis infection in an immunocompromised patient with no history of previous flavivirus infection. The infection due to USUV evolved rapidly since hospital admission thus resulting fatal in few days after symptoms onset and, although not proven, a suspected bacteria co-infection has been hypothesized. Based on these findings, we suggested that when USUV meningoencephalitis is suspected in countries endemic, careful attention should be applied to neurological syndromes during summer months especially among immunocompromised patients

Analisi della trasmissione di SARS-CoV-2: influenza delle condizioni termoigrometriche rispetto al rischio di diffusione del contagio

In questo articolo vengono analizzati i principali meccanismi di diffusione del virus SARS-CoV-2, fornendo elementi utili per la corretta gestione per il contrasto alla diffusione del virus stesso. Lo studio prende le mosse dalla constatazione che, allo stato dell’arte, manca una terminologia rigorosa e univocamente accettata nella letteratura tecnico-scientifica con riferimento alle modalità con cui può avvenire la trasmissione del contagio di SARS-CoV-2 e, in particolare, alle modalità di trasporto cosiddette “droplet” e “airborne”. La corretta analisi dei meccanismi che governano la diffusione del virus non può prescindere da una rigorosa definizione dei termini che entrano in gioco nella descrizione dei fenomeni, da cui discendono importanti indicazioni volte a determinare soluzioni tecniche finalizzate alla minimizzazione del rischio di contagio. Partendo dalla definizione di una terminologia rigorosa ed univoca, attraverso l’applicazione un nuovo modello per lo studio della propagazione del contagio, lo studio, sulla base di valutazioni fisico-matematiche, dà ragione di come il contagio avvenga solo mediante goccioline, sole a poter veicolare efficacemente il virus. Sulla base di queste valutazioni, lo studio analizza il trasporto del virus, incluso nelle goccioline, sulla base dei principi della termo-fluidodinamica, ovvero accoppiando alle equazioni del moto le equazioni che descrivono la variazione di massa per evaporazione. Infatti, la gittata di una goccia emessa da un soggetto infetto, ovvero la distanza di sicurezza da mantenere per minimizzare il rischio di contagio, dipende da numerosi parametri fra i quali, di notevole importanza, il grado igrometrico dell’ambiente in cui questa, la goccia, si trova: da esso, infatti, dipende la velocità di evaporazione e, quindi, la sussistenza della goccia. Pertanto, lo studio dimostra che il controllo del trasporto del contagio non può essere affrontato in assenza di controllo del grado igrometrico dell’ambiente in cui la goccia si muove: infatti, la definizione stessa di distanza di sicurezza perderebbe di significato in quanto la gocciolina potrebbe “sopravvivere” nell’ambiente con elevata umidità, anche per tempi lunghi e realizzando percorsi casuali, qualora le goccioline fossero al di sotto di certe dimensioni. A conclusione dello studio, è riportato un caso di studio che dimostra non solo la correlazione fra grado igrometrico e distanza di sicurezza ma anche che la trasmissione del contagio di tipo airborne, ovvero tramite virioni rilasciati a seguito di evaporazione della goccia, in virtù della loro bassissima concentrazione e del moto di tipo browniano che li caratterizza, abbia una probabilità del tutto trascurabile rispetto alla trasmissione dell’infezione da SARS-CoV-2

Identification of Novel Genetic Loci Associated with Thyroid Peroxidase Antibodies and Clinical Thyroid Disease

Peer reviewe